1. Field of the Invention
The present invention relates to a touch sensing device and a touchscreen device.
2. Description of the Related Art
A touch sensing device, such as a touchscreen, a touch pad, and the like, an input device attached to a display device to provide an intuitive input method to a user, has been widely used in various electronic devices, such as cellular phones, personal digital assistants (PDAs), navigation devices, and the like. In particular, as the demand for smartphones has recently increased, the use of a touchscreen capable of providing various data input methods in a limited form factor has increased.
A touchscreen used in portable devices may be mainly classified as a resistive type touchscreen or a capacitive type touchscreen depending on a method of sensing a touch utilized thereby. Here, the capacitive type touchscreen has advantages in that it has a relatively long lifespan and various data input methods and gestures are easily implementable therewith, such that the use thereof has correspondingly increased. In particular, a multi-touch interface may be more easily implemented with the capacitive type touchscreen as compared to the resistive type touchscreen, such that the capacitive type touchscreen is widely used in devices, such as smartphones, and the like.
The capacitive type touchscreen includes a plurality of electrodes having a predetermined pattern, in which the plurality of electrodes defines a plurality of nodes in which the changes in capacitance are generated by a touch. In the plurality of nodes distributed on a two-dimensional plane, a change in self-capacitance or a change in mutual-capacitance is generated by the touch. Coordinates of the touch may be calculated by applying a weighted average calculation method, and the like, to the changes in capacitance generated in the plurality of nodes. In this case, an analog-to-digital converter (ADC) is used to convert analog signals, such as the changes in capacitance, and the like, generated in the plurality of nodes, into digital signals. Here, as a resolution of the analog-to-digital converter (ADC) is increased, the sensitivity and performance of the touch sensing device are improved. However, when a high-specification analog-to-digital converter (ADC) is used to design a touch sensing device having improved sensitivity and performance, an area of the analog-to-digital converter (ADC) may be increased and manufacturing costs may be increased.
Patent Document 1 relates to a readout circuit unit, having a difference between two sensing voltage values each stored in a sensing block applied thereto by using a sigma delta principle applied to a touchscreen device to generate a delta voltage and provide the delta voltage as an N-bit digital signal. However, Patent Document 1 does not disclose a feature of feeding back voltage depending on the changes in capacitance generated in the touchscreen.